dihydrotestosterone (DHT)

DHT is a turbo-charged version of testosterone. The body takes ordinary testosterone and, with one enzymatic step, makes a hormone that binds the same receptor far more tightly and lingers longer, so it delivers a stronger, more sustained masculinizing push in the tissues where it forms.

DHT is produced from testosterone by the enzyme 5-alpha-reductase, mostly inside target tissues rather than in the bloodstream. It is the dominant androgen for several specific jobs: forming the external male genitalia and prostate before birth, and later driving prostate growth, beard and body hair, and the type of hair-follicle miniaturization that causes male-pattern baldness. Because it binds the androgen receptor with higher affinity than testosterone, even modest local amounts can have powerful effects.

Because DHT drives prostate enlargement and scalp hair loss, drugs that block 5-alpha-reductase (such as finasteride) are used to shrink the prostate and slow balding. The trade-off illustrated by people genetically lacking the enzyme is instructive: they are born with underdeveloped external genitalia yet have normal testosterone, normal muscle, and a normal voice, showing that DHT is essential for some male traits but not all.